Two things then the apostle had asserted with the utmost strength in the preceding verses of the chapter—his burning love for his brethren after the flesh and consequent grief at their low estate and danger; and his sense of their privileges far fuller and stronger than their own, demonstrated above all in his estimate of their Messiah's glory whom they depreciated and had even rejected to their own ruin. This last however is not openly said but unmistakably implied; for the apostle treats their difficulties with the utmost delicacy, caring for their souls with a love truly divine. Whether the expression of his grief then or of that glory of Christ which they refused in unbelief raised the question, which the free grace preached to the Gentiles indiscriminately with the Jews of itself put in the most direct form, whether such a proclamation of grace to every soul, Jew or Greek, be compatible with the special promises to Abraham and to his seed? The Israelite instinctively resented the gospel as annulling his distinctive place of favor, and viewed the apostle's deep concern for their salvation through faith in Jesus as an impeachment of God's pledges to their nation as vouchsafed to their fathers. How could this plighted troth be sure, if the Messiah had come and been rejected by them? if the door was now as open to the Gentile as the Jew Where the value of the promises in either case? Did not the apostle's teaching clash with the trustworthiness of the divine word to Israel? This is fully met now.
“Not however as though the word of God hath failed; for not all those that [are] of Israel [are] Israel; nor because they are Abraham's seed, [are] they all children, but in Isaac shall a seed be called to thee. That is [it is], not the children of the flesh that [are] children of God, but the children of the promise are reckoned for seed; for this word [is] of promise, according to this season. I will come, and Sarah shall have a son. And not only [so], but Rebecca also, having conceived by one, Isaac our father (for not yet having been born, nor having done anything good or bad, in order that the purpose of God according to election should abide, not of works but of him that calleth), it was said to her, The elder shall serve the younger, according as it is written, Jacob I loved, but Esau I hated.
The reasoning is as conclusive as it is concise and clear, founded on proofs from Old Testament facts and words which a Jew certainly could not gainsay. Did he reason from the promises to Abraham, Isaac, and Jacob? From this very history the apostle refutes their unbelieving abuse of all. The word of God therefore retains all its force. Man only, the Jew specially, is proved to be faulty. Their objection assumed that God was bound to bless the entire race in natural descent from Abraham. But this would open the promises to the Ishmaelites. Not so, cries the Jew: the promise is only in the line of Isaac. Then, might the apostle rejoin, the natural descent is an unsound principle; for this embraces the Arabs sprung from Abraham after the flesh no less than the Jews. They themselves therefore to exclude the Ishmaelites must fall back on the promise tied to the line of Isaac. Promise therefore, not flesh, decides. How the answer of the apostle exemplifies the truth of the Jew and circumcision that God praises, stated already in the end of chapter 2, needs no proof. Hence it is equally said of Israel, and of Abraham's seed. It is universally true. Fleshly descent alone insures no inward blessing. The Israelite indeed in whom is no guile is more than one of Jacob's posterity: all of Israel are not Israel, nor are Abraham's seed all children. Compare John 8:37, 39. God must be left free; and He is pleased to call Isaac, not Ishmael after the same sort. The call flows from grace and is inseparable, in the restrictive personal sense here intended, from choice. Far from disputing it, the Jew could not hear the case without falling under its irresistible force; for he wished not to take in the sons of Ishmael and must therefore agree to the necessity of God's call, not mere natural line, in order to constitute an adequately valid claim. And this is made more telling by the striking circumstance that Isaac was born in an exclusively natural way like Ishmael but according to a distinct word of promise on God's part.
The apostle follows up the argument by a still closer instance; for Ishmael was born of a slave, a concubine, Isaac of the wife. But what of Rebecca? She was in no sense a bondmaid, but bore to Isaac twin sons. No case can be conceived therefore more in point. Yet without the children being yet born or having done anything good or ill which could determine between them, God revealed His purpose respecting the younger or lesser of the two, so that election might thus stand fixed and indisputable where His authority is owned.
Hence the apostle contrasts the call of God with works, rather than our faith, so as to cut of the poor semi-Pelagianism of such as Chrysostom of old or Tholuck of late, which would make election governed by the foreseen superiority of one to the other. Language cannot more precisely contradict this, the natural thought (not of natural men only but) of reasoning or imaginative saints. Esau had done no ill to disqualify him, Jacob no good to qualify him; but, before either of the twins was born, God in the exercise of His sovereign will chose that the greater should do service to the lesser. Such was His purpose. Their works had nothing to do with the matter, and are excluded, so as to rest all on the caller, God Himself.
On the other hand, there is no ground favorable to that absolute reprobation which Calvin deduces from this place. Not a syllable is hinted as to hating the unborn Esau in Gen. 25 Man hastily infers reprobation of the one from the choice of the other. This is unfounded. Out of two who have no claim to choose one to a superior place is to exercise will; but to show favor in one case is not therein to condemn the other. They were in themselves both born in sin, as they no doubt grew up in sins. This is to be obnoxious to condemnation, which turns on man's sins, not on God's purpose. It is not Jehovah's word to Rebecca, but by Malachi which speaks of hating Esau. It was at the very close of the Old Testament, after Esau had displayed his unrelenting enmity to Israel. The love to Jacob thus was free; the hatred had moral grounds in Esau.